fix: handle null values in optional fields to prevent value conversion errors

[jasonwbarnett]

Fixes #60

Summary

This PR fixes value conversion errors that occur when the Entitle API returns null values for optional fields like integration, workflow, allowed_durations, and maintainers. The provider now properly handles null values and prevents drift detection when these fields are null in both the configuration and API response.

Changes

• Changed Integration and Workflow fields to pointer types (*utils.IdNameModel) to handle null values
• Added nil checks in Create/Read/Update functions to safely handle null integration and workflow objects
• Updated convertFullResourceResultResponseSchemaToModel function to preserve null values for allowed_durations and maintainers instead of converting them to empty arrays
• Added UseStateForUnknown() plan modifiers to computed name fields within integration and workflow nested attributes to prevent drift on read-only fields
• Removed Computed: true from allowed_durations and maintainers schema - having both Optional and Computed caused value conversion errors during updates
• Fixed Update function to only send Owner and Workflow pointers when populated - prevents 404 errors from API when sending empty structs
• Added TestResourceResourceNullFields acceptance test to verify null handling behavior

Testing

• Added new acceptance test TestResourceResourceNullFields that:
  • Creates a resource with minimal required fields (no allowed_durations, no maintainers)
  • Verifies no drift occurs when re-applying the same configuration
  • Verifies import works correctly without showing drift
• Manually tested import functionality with actual resources
• Verified terraform plan shows "No changes" after import
• Validated bidirectional requestable field updates (true ↔ false)
• Confirmed Update operations succeed without 404 errors

Technical Details

The root cause was that non-pointer struct types in Go cannot represent null values. When the API returned null for optional nested objects like integration or workflow, the Terraform Plugin Framework couldn't convert these null values to the non-nullable utils.IdNameModel struct type.

Additionally, optional fields marked as Computed: true caused Terraform to treat them as "unknown" during update operations, leading to "Value Conversion Error" when trying to convert unknown values to Go slice types.

The fix:

1. Converts Integration and Workflow fields to pointer types with comprehensive nil checks
2. Removes Computed: true from optional list/set fields to prevent unknown value errors
3. Only sends optional fields in Update requests when they have actual values

🤖 Generated with Claude Code

Co-Authored-By: Claude [email protected]